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Take-home Tensile Testing System for Biomechanics Education

Matthew Leineweber

Article Category: Research Article

Volume/Issue: Volume 1: Issue 2

Online Publication Date: Jun 29, 2020

DOI: 10.35459/tbp.2020.000149

Page Range:

expensive lab equipment and allowing a student to learn at his or her own pace outside traditional classroom and laboratory settings ( 1 – 5 ). II. SCIENTIFIC AND PEDAGOGIC BACKGROUND Characterization of material properties is a central component across many scientific and engineering disciplines. In the fields of biomechanics and mechanobiology, the bulk mechanical properties, that is, how materials respond to applied loads, of both biologic tissues and traditional engineering materials are of particular interest. Understanding of these

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Fig 1; The Kelvin–Voigt representation of the SLS model consisted of two elastic spring elements with moduli E1 and E2 and a single dashpot (viscous) element with parameter η. For stress and relaxation tests, the specimen is stretched to a fixed strain value, ε, and the stress σ(t) is recorded as a function of time.

Matthew Leineweber

Fig 1

The Kelvin–Voigt representation of the SLS model consisted of two elastic spring elements with moduli E ₁ and E ₂ and a single dashpot (viscous) element with parameter η. For stress and relaxation tests, the specimen is stretched to a fixed strain value, ε, and the stress σ(t) is recorded as a function of time.

Fig 4; Wiring diagram for the load cell (top left), ultrasound displacement sensor (top right), and Arduino Uno microcontroller. The load cell requires the use of a signal amplifier (left) to increase the output voltage prior to being recorded by the microcontroller. Both sensors run off the Arduino Uno onboard 5-V power supply.

Matthew Leineweber

Fig 4

Wiring diagram for the load cell (top left), ultrasound displacement sensor (top right), and Arduino Uno microcontroller. The load cell requires the use of a signal amplifier (left) to increase the output voltage prior to being recorded by the microcontroller. Both sensors run off the Arduino Uno onboard 5-V power supply.

Fig 2; The lab kits are given to students disassembled. Each kit consists of the (A) leadscrew, (B) frame and hardware, (C) custom end blocks, (D) 3D printed parts, (E) electronics and sensors, and (F) test specimens to conduct a series of 3 separate lab activities exploring concepts pertaining to elasticity and viscoelasticity.

Matthew Leineweber

Fig 2

The lab kits are given to students disassembled. Each kit consists of the (A) leadscrew, (B) frame and hardware, (C) custom end blocks, (D) 3D printed parts, (E) electronics and sensors, and (F) test specimens to conduct a series of 3 separate lab activities exploring concepts pertaining to elasticity and viscoelasticity.

Fig 3; The fully assembled desktop tensile testing system connects to a laptop or desktop computer through the Arduino USB interface. A MATLAB script is used to record the measurement data collected by Arduino. When the leadscrew is turned, the center block travels horizontally.

Matthew Leineweber

Fig 3

The fully assembled desktop tensile testing system connects to a laptop or desktop computer through the Arduino USB interface. A MATLAB script is used to record the measurement data collected by Arduino. When the leadscrew is turned, the center block travels horizontally.

Fig 6; Sample deformation and force plots for the stress and relaxation testing of the silicone rubber specimen. The sample was quickly stretched to a 5.9-cm deformation, held at a constant length for approximately 16 s, and then returned to the original length. The SLS material constants were then determined by performing an exponential linear regression on the decaying force versus time data. This analysis returned parameters E1 = 57.9 N/m, E2 = 14.4 N/m, and τ = 2.0 s–1.

Matthew Leineweber

Fig 6

Sample deformation and force plots for the stress and relaxation testing of the silicone rubber specimen. The sample was quickly stretched to a 5.9-cm deformation, held at a constant length for approximately 16 s, and then returned to the original length. The SLS material constants were then determined by performing an exponential linear regression on the decaying force versus time data. This analysis returned parameters E ₁ = 57.9 N/m, E ₂ = 14.4 N/m, and τ = 2.0 s^–1.

Fig 5; The load cell was calibrated by fitting the linear relationship to the raw voltage from the load cell to the expected force produced by stretching a spring with a known rate constant. The noise in the “true force data” is a result of the low resolution of the ultrasonic displacement sensor.

Matthew Leineweber

Fig 5

The load cell was calibrated by fitting the linear relationship to the raw voltage from the load cell to the expected force produced by stretching a spring with a known rate constant. The noise in the “true force data” is a result of the low resolution of the ultrasonic displacement sensor.

Fig 7; Pre- and postlab quiz scores show a significant improvement after completion of the labs. The small cohort of students representing the 1-year follow-up quiz for students who did not have access to any lab activities performed similarly to the prelab scores.

Matthew Leineweber

Fig 7

Pre- and postlab quiz scores show a significant improvement after completion of the labs. The small cohort of students representing the 1-year follow-up quiz for students who did not have access to any lab activities performed similarly to the prelab scores.

Using Plant Cells of Nitellopsis obtusa for Biophysical Education

Vilmantas Pupkis,

Rokas Buisas,

Indre Lapeikaite, and

Vilma Kisnieriene

Article Category: Research Article

Volume/Issue: Volume 2: Issue 1

Online Publication Date: Nov 24, 2020

DOI: 10.35459/tbp.2019.000130

Page Range: 18 – 29

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Fig 3; Extracellular recording system. A complete block scheme (top) and a partial photo (bottom). A cell (b) is put along the chamber (a). The gaps between the chamber's compartments (c) are isolated with petroleum jelly (d). The electrodes are made from sewing pins (e) and fixed to the chamber with plasticine (f). The e-Biol universal data acquisition and control system (26) is used for signal amplification (g) and digitization (h). The data acquisition system is controlled by a personal computer (i). The conventional 1.5V battery (j) is used for manual electrical stimulation.

Vilmantas Pupkis,

Rokas Buisas,

Indre Lapeikaite, and

Vilma Kisnieriene

Fig 3

Extracellular recording system. A complete block scheme (top) and a partial photo (bottom). A cell (b) is put along the chamber (a). The gaps between the chamber's compartments (c) are isolated with petroleum jelly (d). The electrodes are made from sewing pins (e) and fixed to the chamber with plasticine (f). The e-Biol universal data acquisition and control system (26) is used for signal amplification (g) and digitization (h). The data acquisition system is controlled by a personal computer (i). The conventional 1.5V battery (j) is used for manual electrical stimulation.